Magnetic writing screens are popular toys with young children. These toys consist of a screen in a housing containing a dispersion medium. The dispersion medium contains magnetic material such as iron powder. A pen having a magnetic tip is drawn across the screen causing the dispersion medium to be drawn up against the underside of the screen. By tracing the pen across the screen, the user can create drawings and figures. A sliding mechanism is usually employed to remove the dispersion medium from the underside of the screen to erase the drawings and begin anew.
The dispersion medium must be able to be attracted by the relatively weak magnet of the pen. Also, the dispersion medium must create good contrast and clear drawing lines. The dispersion medium must adequately cling to the underside of the screen but be easily removed under the action of a device such as a sliding mechanism. The complete removal of the dispersion medium from the underside of the screen is necessary to insure the long lasting use of the toy.
The prior art discloses several types of dispersion mediums used in magnetic writing screen toys. Problems with the prior art include the toxicity of the dispersion medium. Because it is possible that a child can break the housing, the dispersion medium can leak from the toy. For this reason, it is very important that the substance be non-toxic. Also, some dispersion mediums have poor contrast between black and white. The result is that the drawn line is blurred and broken. Some dispersion mediums have been developed which have very good contrast when drawn on a screen. However, these dispersion mediums are hard to erase from the screen. Eventually, permanent black spots appear on the screen after the toy has been used multiple times. Once this occurs, drawings made in the future are not as clear.
It is an object of the invention to provide a magnetic dispersion medium that is non-toxic.
It is another object of the invention to provide a magnetic dispersion medium that provides good contrast when lines are drawn on the magnetic screen.
It is yet another object of the invention to provide a liquid dispersion medium that is easily erased from the screen.
It is yet another object of the invention to provide a dispersion medium that can be used to drawn lines on the screen hundreds of times without creating permanent black marks on the screen.
These and other objects of the invention will become apparent after reading the disclosure of the invention.